The present invention relates to liquid-ejecting heads, liquid-ejecting apparatuses, and methods for manufacturing liquid-ejecting heads, and relates to, for example, a thermal printing head. According to the present invention, insulating films on wafers are removed to form shallow grooves along at least rows of energy transducers. In this manner, the grooves can prevent various types of damage due to cracking and chipping even during high-speed dicing.
In printers provided with printing heads ejecting ink droplets, energy transducers convert electric energy into energy for ejecting ink. Heating devices are used as the energy transducers for thermal printing heads.
In thermal printing heads, heating devices heat ink contained in ink chambers to generate bubbles, and the ink droplets are ejected from nozzles by the pressure of bubbling.
In such a printing head, heating devices and a driving circuit are integrated densely on a semiconductor substrate, resulting in high-resolution printing. Moreover, the heads are efficiently produced through semiconductor manufacturing processes: Heating devices and driving circuits for a plurality of chips are integrated on a semiconductor substrate, or wafer; the substrate is cut into chips; and ink chambers and nozzles are provided on the chips.
FIG. 1 is a plan view of a semiconductor substrate manufactured by a known process. In the process, a 6-inch silicon wafer 1, for example, is sequentially processed to form, at a predetermined pitch, rectangular regions 2, each of which includes heating devices and a driving circuit for one chip. In FIG. 1, the size of the regions 2 is illustrated larger than their actual size relative to the silicon wafer 1.
FIG. 2 shows cutting regions 3 formed between the regions 2 during processing of the silicon wafer 1 in a manufacturing process of the printing heads. As shown in a cross-sectional view of FIG. 3, a protective film 4 for preventing penetration of ink, and an insulating film 5 under the protective film 4 are removed from the silicon wafer 1 to form cutting region 3 wider than a blade used for dicing. In the example shown in FIG. 3, the cutting region 3 has a width of 140 μm for a blade width of 50 μm.
In the process, the silicon wafer 1 is held on a stage of a dicing machine. The stage or the blade rotating at high speed is driven such that the blade cuts the silicon wafer 1 substantially at the center of the cutting regions 3 into chips. In this step of fabricating printing heads, a stream of deionized water is provided to the areas to be cut in order to cool the blade and wash away cutting debris.
In this dicing step, an impact due to increasing the cutting speed causes cracking and chipping at the chip edges. FIG. 4 is a plan view of an edge of the chip in FIG. 3. The chip is formed by cutting the silicon wafer 1 with a blade 50 mm in diameter rotating at a speed of 30,000 rpm and fed at a speed of 30 mm/sec, and has chipped portions of approximately 17 μm. The relative speed between the blade- and the silicon wafer 1 under these conditions is given by 50 [mm]×3.14×60×30,000/1,000,000=282 km/h. The collision of the blade with the silicon wafer at high speed is a possible cause for cracking and chipping.
In a printing head, ink contained in ink chambers is heated by the heating devices on the chip, and droplets thereof are ejected as a result. When cracking or chipping occurs in the chip, the ink can penetrate into the chip and may cause instability of semiconductor performance. When ink is introduced to the ink chambers from a side face of the chip, the fluid resistance in the ink passage connected to the ink chambers may change due to cracking or chipping, resulting in slight changes in print quality. Furthermore, when the chipping fragments remain on the chip surface, these fragments can damage the chip surface during forming of the ink chambers. In the event that the damage from the chipping fragments reaches inside the chip, ink will penetrate into the chip, and a wiring pattern or the like may be damaged in the case of severe damage.
To prevent cracking and chipping of the chip, the cutting speed in the process of manufacturing printing heads should be slower than that in a process of manufacturing standard integrated circuits.
A method for dicing standard integrated circuits is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 6-275713, in which grooves deeper than the depth of devices, such as transistors, are formed on both sides of the cutting regions in order to prevent the propagation of cracks during cutting.
In a manufacturing process of printing heads in which a 6-inch silicon wafer is cut along 60 longitudinal lines and 12 transverse lines to form chips at a cutting speed of 5 mm/sec, the time required for cutting is 60×12×(150/5)/3,600=6 hours. Thus, the known dicing step for cutting chips at low speed to avoid cracking and chipping disadvantageously takes time.
When the method disclosed in Japanese Unexamined Patent Application Publication No. 6-275713 is applied as a solution for this problem, it requires an additional etching step to form grooves deeper than the devices. Besides, since it is not possible to avoid the chipping fragments, damage to the chip surfaces from the fragments is inevitable.